Bill de Blasio, center, looks on, New York City Schools Chancellor Carmen Farina, right, talks to President of the United Federation of Teachers Michael Mulgrew.AP

Fresh cause for city parents to fret: For the second straight year, the share of teachers winning tenure has ticked up.

Some 64 percent got the OK this year, meaning they’ll be nearly impossible to fire as long as they want to keep their jobs.

That’s only slightly higher than last year’s 60 percent rate — but a marked jump from the 53 percent figure the year before, Mike Bloomberg’s last year as mayor.

Bloomberg wanted to be able to oust teachers who can’t teach. That’s a key reason why, on his watch, the tenure-approval rate fell steeply from the days when nine out of 10 teachers got lifetime protection.

But for Mayor de Blasio, it’s more important to please the teachers unions — which donate so generously to his causes. And the unions don’t want any teachers fired, no matter how awful.

Indeed, de Blasio’s focus has been on keeping teachers from quitting, not weeding out the ineffective ones.

Do kids suffer? You decide: While nearly two out of three teachers made it into the “can’t-fireme” club, nearly two out of three students flunked the state math tests, and seven in 10 bombed reading.

The toll on blacks and Hispanics has been especially high: More than three out of four were unable to pass the tests.

De Blasio and the unions try to pin all the blame on the kids and their families.

On Saturday, the mayor asked union members: “Remember those days when the people who did the work” — i.e., teachers — “were somehow [accused of] causing the problem?” No more: “Together, we are changing that reality.”